It is known to equip electronic devices with so-called step-down voltage converters. Particularly, but not exclusively, in relation to portable electronic devices, the provision of the step-down converters serves to improve efficiency of an electronic system employed by the device, thereby increasing cycle time of a battery used by the device.
However, some electronic devices have a number of modes of operation, each mode having different power consumption requirements, for example, a radio-frequency communications apparatus can have an active mode and a standby mode, each mode having a distinctive loading regime. Also, it has been recognised that inefficiencies arise when a single voltage regulation scheme is employed to satisfy current demands associated with the different power consumption requirements. In this respect, a pulse frequency modulation scheme is preferable for low power demand modes and a pulse width modulation scheme is preferable for higher power demand modes to maintain maximum battery lifetime. Consequently, known step-down voltage conversion circuitry typically employs a first pulse frequency modulation circuit and a second pulse width modulation circuit to control an output power signal, the first circuit being selectable in preference to the second circuit and vice versa in response to a software-controlled “pin”, such as a terminal of an integrated circuit. The software determines the mode of operation of the device and sends a control signal to the pin to select the first or second circuit to control the output power signal.
However, the provision of the control pin and the software adds a level of complexity, and hence an overhead, to the step-down voltage converter that is desirable to be avoided.